1. Field of the Invention
The present invention relates generally to a mechanism for locking one or more boards onto a chassis or a casing, and in particular, to a mechanism for locking one or more boards, on each of which electronic components are mounted, onto the chassis or casing of an electronic device.
2. Description of the Related Art
In an electronic device such as a computer, which is composed of a number of units such as a power supply unit and logic units and/or packages such as I/O cards, it is important, in terms of the functionality of the device, that they can be mounted onto or dismounted from the chassis even while the device is running. Furthermore, as the operating frequencies of the LSI chips such as the processors mounted on such a computer keep rising, it is becoming increasingly important to devise a method of locking the metallic parts of these units or packages such as locking brackets therefore onto the computer's chassis or the electrically conductive material provided on it, while ensuring a secure contact between them.
One way of doing so is to use ordinary screws, which entails several issues. First, one needs a tool to tighten the screws. Also, there is the possibility of a short circuit if a screw drops onto an electrically live part. Furthermore, in cases where a jig is required to tighten the screws and others, it is necessary to attach the jig to the device or to keep the jig somewhere safe so that it can be easily retrieved.
Because of these issues, demand has been increasing for a mechanism for locking units or packages that requires no screws, tools or jigs. For example, Japanese Unexamined Patent Application Publication No. 2003-318575 (JP-A-2003-318575) discloses, as a locking mechanism for locking boards such as PCI cards onto the chassis of a personal computer or a similar piece of equipment without using a tool, a locking mechanism comprising a base plate that is directly placed on the chassis, a stopper plate that presses and holds down a metal piece for locking the boards onto the chassis, and a lock plate that keeps the stopper plate in the hold-down position. Further, Japanese Unexamined Patent Application Publication No. 2007-184359 (JP-A-2007-184359) discloses, as a locking mechanism for locking units or packages onto the chassis of an electronic device or a similar piece of equipment without using a tool, a locking mechanism comprising a mechanical part for pressing and holding a metal piece (such as a bracket) in place that belongs to each such unit or package, a cylindrical supporter for rotating this mechanical part, and a screw or a set of screws for holding the mechanical part so that it will not fall off the supporter.
One of the disadvantages of the locking mechanism disclosed in JP-A-2003-318575 lies in the fact that, while it does not require any tools, it does require many components such as a base plate, a stopper plate, a coil spring, and a lock plate, which pushes up the component cost. Furthermore, it involves a rather complex operation: two or more steps are needed to securely lock the boards.
Likewise, the locking mechanism disclosed in JP-A-2007-184359, which does not require any tools and involves only one step of operation to securely lock the units or packages, has similar problems if there is more than one board to lock: It is necessary to prepare as many locking mechanisms as the number of boards to lock, which leads to an increase in the number of steps in operation and also pushes up the component cost.